The gastrointestinal (GI) tract, also called the alimentary canal, is a long tube through which food is taken into the body and digested. The alimentary canal begins at the mouth, and includes the pharynx, esophagus, stomach, small and large intestines, and rectum. In human beings, this passage is about 30 feet (9 meters) long.
Small, ring-like muscles, called sphincters, surround portions of the alimentary canal. In a healthy person, these muscles contract or tighten in a coordinated fashion during eating and the ensuing digestive process, to temporarily close off one region of the alimentary canal from another region of the alimentary canal.
For example, a muscular ring called the lower esophageal sphincter (or LES) surrounds the opening between the esophagus and the stomach. Normally, the lower esophageal sphincter maintains a high-pressure zone between fifteen and thirty mm Hg above intragastric pressures inside the stomach.
In the rectum, two muscular rings, called the internal and external sphincter muscles, normally keep fecal material from leaving the anal canal. The external sphincter muscle is a voluntary muscle, and the internal sphincter muscle is an involuntary muscle. Together, by voluntary and involuntary action, these muscles normally contract to keep fecal material in the anal canal.
Dysfunction of a sphincter in the body can lead to internal damage or disease, discomfort, or otherwise adversely affect the quality of life. For example, if the lower esophageal sphincter fails to function properly, stomach acid may rise back into the esophagus. Heartburn or other disease symptoms, including damage to the esophagus, can occur. Gastrointestinal reflux disease (GERD) is a common disorder, characterized by spontaneous relaxation of the lower esophageal sphincter.
Damage to the external or internal sphincter muscles in the rectum can cause these sphincters to dysfunction or otherwise lose their tone, such that they can no longer sustain the essential fecal holding action. Fecal incontinence results, as fecal material can descend through the anal canal without warning, stimulating the sudden urge to defecate. The physical effects of fecal incontinence (i.e., the loss of normal control of the bowels and gas, liquid, and solid stool leakage from the rectum at unexpected times) can also cause embarrassment, shame, and a loss of confidence, and can further lead to mental depression.
In certain surgical systems, radiofrequency energy is applied to tissue at different tissue levels to create multiple tissue lesions. Application of such energy requires continuous monitoring of certain tissue and/or device parameters to ensure that the tissue is not heated to such extent that damaging burning of tissue occurs. Thus, these systems monitor tissue temperature and/or device electrode temperature and provide safety features to cut off energy flow if the tissue temperature rises too high. However, with the application of radiofrequency energy, there is a fine point in which tissue is treated to form lesions and beneficially alter structure of the tissue, e.g., alter the structure of the sphincter muscle, while not being ablated.
Ablation of tissue can be generally defined as a removal of a part of tissue. Radiofrequency energy to ablate tissue has been used for various tumor treatments, destroying tissue and creating tissue necrosis. However, avoiding tissue ablation may be beneficial in treating the gastrointestinal tract in the foregoing or other procedures. Therefore, it would be advantageous to provide a system of applying radiofrequency energy to tissue at a power setting and time duration which causes thermal effect to tissue to create tissue lesions along a series of tissue levels but avoids ablation or burning of tissue.
However, in avoiding tissue ablation, care needs to be taken to ensure that tissue is not undertreated. In other words, in attempts to prevent overheating of tissue which causes ablation, the system needs to conversely ensure that tissue is not under-heated and thus not therapeutically treated. Therefore, the need exists for a system that applies radiofrequency energy to tissue between these two energy levels.